Six-Qubit Decoherence-Free State Measurement Method and its Application to Development of Authenticated Quantum Secure Direct Communication Protocol

This paper proposes a measurement method capable of distinguishing six-qubit decoherence-free states. In addition, based on this measurement method, the paper presents an authenticated quantum secure direct communication (AQSDC) protocol that is simultaneously robust against both collective dephasing noise and collective rotation noise. This AQSDC protocol enables a sender to transmit secure and authenticated messages to a receiver via one-step quantum transmission without using classical channels. The new measurement method enables the qubit efficiency of the AQSDC protocol to be superior to those of existing AQSDC protocols. The analyses presented herein demonstrate that the AQSDC protocol is secure and effective.